Unexpected errors in C++ program?

[Raman009]

Here is the program code:

#include<iostream>
int main() {
cout<<"Hello World";
return 0;
}

Errors using g++ in terminal :

[Raman@Fedora CPP]$ g++ hello.cpp
hello.cpp: In function ‘int main()’:
hello.cpp:3:1: error: ‘cout’ was not declared in this scope

This is first time I am using g++.I am not able to remove these errors .plz help

[Adunaic]

C++ uses namespaces (Have a quick google)

The error is correct, 'cout' has not been declared. The function is std::cout. If you put this in it will work.

You can avoid typing std:: all the time by putting:

using namespace std;

after your #includes.

Then it will work.


Just to make sure it is clear. It should be:

#include<iostream>
int main() {
  std::cout<<"Hello World";
return 0;
}

or

#include<iostream>
using namespace std;
int main() {
  cout<<"Hello World";
return 0;
}

[Raman009]

Thanks , It has successfully compiled the file and a new file named a.out has been created.
How to run this?

[briand]

1) you'll probably want to rename it to something else, other than a.out
a) mv a.out newname

2) chmod +x newname

3) ./newname

[Raman009]

a) mv a.out newname //changes the name of a.out

2) chmod +x newname //changes the mode of file to executable

3) ./newname //executes the file

I think i have understood everything right...Thanks

[Adunaic]

Thanks , It has successfully compiled the file and a new file named a.out has been created.
How to run this?

You should find that it is executable by default so you should not need to follow the steps that briand gave.

If I were you I would specify the name of the output file when you compile it. See below:

g++ hello.cpp -o hello.exe
./hello.exe

That will run your program and you should see

Hello World[Raman@Fedora CPP]$

If you want a new line after "Hello World" change

std::cout<<"Hello World";

to

std::cout<<"Hello World" << std::endl;

If you have not got a book on C++ I would recommend: "Sams Teach Yourself C++ in One Hour a Day" I found it excellent.

[Raman009]

g++ hello.cpp -o hello.exe
./hello.exe

If you have not got a book on C++ I would recommend: "Sams Teach Yourself C++ in One Hour a Day" I found it excellent.

Thanks ,this method is quicker than the previous one..

[rclark]

You could have ran the application: ./a.out

Also in linux you don't need to '.exe' . That's a Windows thing.

$g++ hello.cpp -o hello

...

$ ./hello

[Raman009]

Thanks for replying